#include <stdio.h>
#include <unistd.h>
#include <string.h>
int main(int argc,char *argv[]){
//  int i;
//  for(i=0;i<argc;i++){
//    printf("argv[%d]->%s\n",i,argv[i]);
//  }


// int i;
// for(i=0;argv[i];i++)  #如果可以运行说明存在null值
// {
//   printf("argv[%d]->%s\n",i,argv[i]);
// }
  if(argc!=2){
    printf("Usage:%s -[a,b,c,d]\n",argv[0]);
    return 1;
  }  
  if(strcmp(argv[1],"-a")==0){
    printf("This is function1\n");
  }
  else if(strcmp(argv[1],"-b")==0){
    printf("This is function2\n");
  }
  
  else if(strcmp(argv[1],"-c")==0){
    printf("This is function3\n");
  }
  else if(strcmp(argv[1],"-d")==0){
    printf("This is function4\n");
  }
  else{
    printf("no This function\n");
  }
}
